/Engine/Source/Runtime/Engine/Classes/Kismet/KismetInternationalizationLibrary.h
This function is a sledgehammer, and will set both the language and locale, as well as clear out any asset group cultures that may be set.
True if the culture was set, false otherwise.
static bool SetCurrentCulture ( const [FString](API\Runtime\Core\Containers\FString) & Culture, const bool SaveToConfig )